Resistance exercise equipment now in use in commercial fitness facilities consists almost exclusively of free weights and selectorized or stacked weight cable machines. This type of equipment has the advantage of a relatively low initial cost and simplicity of construction. However, such resistance exercise equipment does not provide the user the most effective method of building stronger muscles or obtaining the equivalent muscle building results in less time.
Various complex computer operated devices have been proposed which have these benefits, but they have not found favor in the marketplace for a variety of reasons, not the least of which is the considerable cost thereof.
The present invention is specifically designed to bridge the rather large gap which exists between weighted exercise equipment and costly, complex computer operated exercise machines. This is accomplished by eliminating the use of weights or gravity forces while at the same time making it possible to permit high velocity, sports specific training. Further, the present invention provides what is known as a "heavy negative" option previously available only in computer operated devices or with partner assistance in the case of free weights.
"Heavy negative" is a method of resistance training in which the resistance to extension of the muscle is greater than the resistance to contraction of the muscle. It is a proven method of increasing the work load and directly building increased strength in a much shorter period of time. Extension resistance can be twenty to forty percent greater than contraction resistance depending upon the muscle being exercised.
Another advantage of this invention is that it is suitable for rehabilitation purposes. This follows because of the fact that the user can set very light resistances. Further, small changes in resistance can be made with digital dial-type controls.
Among earlier attempts, U.S. Pat. No. 2,823,896 to Hood discloses the use of a fluid coupling and a variable speed prime mover. This patent illustrates a method for positioning a load which is connected to the output shaft of the fluid coupling by varying the input speed to the fluid coupling, but it differs in structure from the present invention since the fluid coupling is mounted in the high torque portion of the system rather than in the low torque, high speed portion of the system. U.S. Pat. No. 2,823,896 to Hood utilizes controls which are not designed to allow the device to perform as a variable resistance training device.
U.S. Pat. No. 4,842,274 to Oosthuizen et al. discloses a device which provides a substantially constant resistance to user motion by maintaining a high speed differential between the motor and the cable drum. This can only be achieved by placing the hydraulic coupling in the high torque, low speed portion of the system, much like Hood U.S. Pat. No. 2,823,896. As previously noted, the present invention mounts the hydraulic coupling in the low torque, high speed portion of the system. This provides the advantage of using a prime mover which is a fraction of the size that would otherwise be required thereby also lowering the energy operating cost. Additionally, the present invention permits one small size fluid coupling to meet the full range of tension requirements in contrast to Oosthuizen et al. U.S. Pat. No. 4,842,274.
With Oosthuizen et al. U.S. Pat. No. 4,842,274, it is necessary to use different size fluid couplings for different force ranges which is clearly undesirable for meeting a wide range of operating parameters in various exercise devices. Finally, the present invention produces a safe, natural feeling exercise in both extension or eccentric and contraction or concentric movements without a multiplicity of sensors and controls in contrast to the exercise equipment that has been available and is disclosed in the prior art.
As for one other patent, U.S. Pat. No. 5,015,926 to Casler discloses a motorized system with an electrically controlled metallic powder or fluid clutch and feedback system which measures torque (force) and speed as well as direction of motion. The present invention differs in that the hydraulic coupling receives no feedback signal, the performance curve of the fluid coupling is fixed, and the control variable is the speed of the prime mover which drives the fluid coupling.